Radiological image capturing apparatus and radiological image capturing system

ABSTRACT

There is described a radiological image capturing apparatus, which makes it possible to obtain a good X ray image in which contrast of the peripheral portions are emphasized by employing the Talbot interferometer method and the Talbot-Lau interferometer method. The apparatus is provided with an X-ray tube, a multi-slit member, a first diffraction grating, a second diffraction grating and an X-ray detector. The second diffraction grating contacts the X-ray detector. A distance L between the multi-slit element and the first diffraction grating is set to be not less than 0.5 m, a distance Z 1  between the first diffraction grating and the second diffraction grating is set to be not less than 0.05 m, and a slit interval distance d 0  of the multi-slit element is set to be not less than 2 μm. With the settings, the abovementioned good X-ray image can be obtained by using the Talbot-Lau interferometer system.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 13/781,840, filed on Mar. 1, 2013. The Ser. No.13/781,840 is a continuation of Ser. No. 12/527,673, filed on Aug. 18,2009, the entire contents of which are incorporated herein by referenceand priority to which is hereby claimed. The Ser. No. 12/527,673 is aU.S. national stage of application No. PCT/JP2008/052422, filed on 14Feb. 2008, the entire contents of which are incorporated herein byreference and priority to which is hereby claimed. Priority under 35U.S.C. §119(a) and 35 U.S.C. §365(b) is claimed from JapaneseApplication No. 2007-041437, filed 21 Feb. 2007, Japanese ApplicationNo. 2007-041440, filed 21 Feb. 2007, and Japanese Application No.2007-041446, filed 21 Feb. 2007, the disclosures of which are alsoincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a radiological image capturingapparatus and a radiological image capturing system, and specificallyrelates to such a radiological image capturing apparatus that employs aTalbot-Lau interferometer method and such a radiological image capturingsystem that applies various kinds of processing to an image captured bythe radiological image capturing apparatus.

TECHNICAL BACKGROUND

In recent years, the morbidity rate of the rheumatic disease in Japanhas reached to 1% of the national population, and accordingly, therheumatic disease has been regarded as a kind of a folk disease atpresent. An abrasion loss at a cartilage portion (destruction ofcartilage) and/or subtle changes of a bone shape and a bone trabeculaeare observed as its early symptoms, and then, at the time when thesymptoms have worsened, considerable changes of shape of the bonesections can be observed significantly. Accordingly, by observing theshape of cartilage portion and subtle changes of the bone shape and thebone trabeculae, it is possible to make a diagnosis with respect to thedisease situation of the rheumatic disease at its early stage.Considering the actual condition that only medical treatments forstopping the progress of the symptoms are currently available as themedical treatments for the rheumatic disease, it is important to detectthe rheumatic disease at its early stage and to speedily shift thepatient into the phase of applying the medical treatments.

However, the above-mentioned early symptoms of the rheumatic diseasehave been hardly detected by observing the X-ray photographic image,which has been widely accepted as a simple and convenient inspectionmethod, and accordingly, it has been difficult for a doctor or the liketo determine whether or not the rheumatic disease has actuallydeveloped.

On the other hand, in recent years, instead of the radiographic imagesacquired by radiographing the patient, images acquired by employing theMRI (Magnetic Resonance Imaging) has been considered as a tool formaking diagnosis, in order to detect the changes of cartilage tissues.Further, recently, in the field of the radiographic image capturingtechnologies, there has been reported such a technology that extracts aradiant beam, which straightly progress in parallel, so that theabove-extracted radiant beam are used for capturing images of thecartilage portion concerned. However, since the patient has been heavilyburdened with the MRI photographing operation from the viewpoint of thecost and time required for making a diagnosis, it has been difficult toperform the MRI photographing operation in the framework of the regularphysical examination. Therefore, there has been such a problem that ithas been difficult to periodically perform the MRI photographingoperation so as to observe (inspect) the changes of the joint portions,such as fingers, etc., over time, as a longitudinal diagnosis.

Further, since a huge image-capturing installation is necessary forconducting the image-capturing operation that employs the radiant beam,and, sometimes, several tens of minutes are required for completing theimage-capturing operation, it has been virtually impossible for ageneral-purpose medical facility to employ the radiant beam forconducting the image-capturing operation. Due to the present situationsas aforementioned, it has been desired to make it possible to simply andeasily make a diagnosis on the diseases of cartilage portion at itsearly stage, such as a subtle change in a shape of joint portion, asubtle change in the bone shape, a swelling, etc.

For instance, in order to make a diagnosis on the case of the rheumaticdiseases at its early stage, it is indispensable to capture such aradiographic image that has a high sharpness being sufficient forrecognizing a subtle change of a symptom in the patient, representedthereon. As the radiological image capturing apparatus that can capturea radiographic image having a sufficiently high sharpness, there hasbeen well-known the technology for capturing a phase contrast image byemploying the radiological image capturing apparatus, for instance, setforth in Patent Document 1. According to the technology set forth inPatent Document 1, even for such a subject whose X-ray absorbing rate isspecifically lower than other subjects to such an extent that itsradiological image having a sufficient contrast cannot be formed byemploying the normal X-ray absorbing action, it has been possible toobtain such an radiological image in which contrast of the peripheralportions (edge portions) are specifically emphasized. Further, it hasbee possible to apply the abovementioned technology not only to jointdisorders, which are represented by the rheumatic disease, but also tovarious kinds of sections, such as a breast image capturing operationthat should be capable of detecting a micro calcification from a breast,most of which is formed by a soft tissue, an operation for radiographinga child body, almost bones of which are cartilages, etc.

Further, as the technology for further emphasizing the contrast of theperipheral portions of the subject, for instance, Patent Document 2 setsforth an X ray radiographing apparatus employing the Talbotinterferometer method based on the Talbot effect caused by thediffraction grating. Still further, Non-patent Document 1 sets forth anX ray radiographing method employing the Talbot-Lau interferometermethod, which is improved from the Talbot interferometer method.

-   [Patent Document 1] Tokkai 2004-248699 (Japanese Laid-open    Non-Examined Patent Publication)-   [Patent Document 2] WO 2004-058070 (International Publication)-   [Non-patent Document 1] “RECENT DEVELOPMENT OF X RAY PHASE IMAGING”    written by Atsushi Momose, Medical Imaging Technology, Japanese    Society of Medical Imaging Technology, November, 2006, vol. 24, No.    5, page 359-366

However, since the radiant beam X ray source, which requires a specialfacility, is employed in the Talbot interferometer method set forth inPatent Document 2, there has been a problem that it is virtuallyimpossible for general-purpose medical facilities, widely exiting in thesociety, to employ the Talbot interferometer method. In addition, insuch the general-purpose medical facilities, it has been assumed thatlow energy X rays are to be irradiated onto the subject. This isbecause, the phase contrast effect, acquired by employing the low energyX rays, is relatively great, and the absorbing contrast effect, acquiredby employing the conventional X rays radiological imaging, is relativelystrong. However, since the excessively low energy X-rays tend to beabsorbed into the human body, and accordingly, since an amount of the Xrays arriving at a detector is relatively small, it is necessary toincrease the dose of radiation exposure in order to acquire anappropriate S/N (Signal to Noise) ratio at the detector, resulting in anincrease of the X-ray exposure. Further, the increase of the X-rayexposure will cause an extension of the image capturing time interval.However, it is difficult to make the movement of the human body, servingas the subject, freeze for a long time during the image capturing timeinterval. Then, as a result of the movements of the subject during theradiographing, an X-ray image in which the peripheral sections of thesubject are blurred would be captured, and accordingly, an advantageouscharacteristic of the Talbot-Lau interferometer that can emphasize thecontrast of peripheral sections of the subject would be deteriorated.

On the other hand, if the energy of the X rays to be irradiated onto thehuman body is excessively high, it has been acquired such a knowledgethat an image contrast being sufficient for depicting bone tissues andsoft tissues that constitute the human body cannot be obtained.Accordingly, there has been a problem that an X ray image, which issufficiently usable for making a diagnosis on the human body, serving asthe subject, cannot be obtained, unless the contrast in the X ray imagecan be obtained.

As abovementioned, when the radiological image capturing apparatus inconformity with the Talbot interferometer method is employed for themedical purpose, a usable range of the X ray radiation energy (preciselyspeaking, average energy) is relatively narrow. In addition, in order togenerate the Talbot effect so as to realize the Talbot interferometermethod, various kinds of strict limitations are applied to a distancebetween a first diffraction grating and a second diffraction grating, aninterval (grating period) between diffraction elements constituting theeach of the diffraction gratings, etc., as detailed later. Therefore, inorder to apply the Talbot interferometer method to an operation forradiographing the various kinds of sections in the human body,specifically for such the sections that are hardly captured by the X-rayimage capturing method, such as the cartilage tissue, etc., theradiological image capturing apparatus should be configured so as tofulfill the extremely strict conditions.

Further, according to the Talbot-Lau interferometer method set forth inNon-patent Document 1, a multi-slit element is disposed between the Xray source to be employed in the Talbot interferometer method and thesubject. Since the X ray emitting source is converted to multi (plural)radiant sources by employing the multi-slit element, it is possible toeffectively utilize the Talbot effect, even if the X ray tube having alarge focal diameter is employed in the apparatus. However, thestructure and configuration of the concerned apparatus become morecomplicated than ever, and, further, since various kinds of conditions,such as positional relationships between the multi-slit element and theother elements, etc., are added as new limitations for configuring theapparatus, the structural conditions for the concerned apparatus becomestill more stricter than ever, and it is required for the concernedapparatus to fulfill such the extremely strict conditions.

On the other hand, a dose of X rays, to be irradiated onto the subjectby the radiological image capturing apparatus employing the Talbotinterferometer method, is relatively small, compared to that to beirradiated by the other radiological image capturing apparatus employingthe Talbot-Lau interferometer method. However, since the X rays areirradiated by a single X-ray emitting source, the radiological imagecapturing apparatus employing the Talbot interferometer method has suchthe advantage that a very clear X-ray image, sharpness of which is veryhigh, can be obtained. Whereas, since the X ray emitting source isconverted to the multi (plural) radiant sources by employing themulti-slit element, the Talbot-Lau interferometer method is inferior tothe Talbot interferometer method in sharpness of the reproduced X rayimage to some extent. However, since it is possible in the Talbot-Lauinterferometer method to irradiate relatively high energy X rays ontothe subject, compared to the Talbot interferometer method, theradiological image capturing apparatus employing the Talbot-Lauinterferometer method has such the advantage that the X-rayradiographing operation can be completed within a shorter time thanever.

Further, if a single radiological image capturing apparatus is soconstituted that the abovementioned two methods are provided within thesingle apparatus so as to make it possible to selectively change them toeach other, for instance, by selecting one of the methods correspondingto the current purpose of capturing the X-ray image, it becomes possibleto obtain the X-ray image to which the advantage of the selected methodis fully applied, resulting in a very convenient apparatus. Stillfurther, if the apparatus concerned is constituted as abovementioned, itbecomes possible to appropriately make a diagnosis by adaptivelyselecting either the Talbot interferometer method or the Talbot-Lauinterferometer method.

As aforementioned, it has been desired that the Talbot interferometermethod or the Talbot-Lau interferometer method is employed foroperations not only for capturing X-ray images of the joint disorders,which are represented by the rheumatic disease, but also for capturingX-ray images of various kinds of sections in human body, such as thebreast image capturing operation that should be capable of detecting themicro calcification from the breast, most of which is formed by the softtissue, an operation for radiographing the child body, almost bones ofwhich are cartilages, etc. However, in order to achieve theabovementioned goals, it is indispensable to configure the apparatus soas to fulfill such the extremely strict conditions as aforementioned.

SUMMARY OF THE INVENTION

To overcome the abovementioned drawbacks in conventional radiologicalimage capturing apparatuses and systems, it is one of objects of thepresent invention to provide a radiological image capturing apparatuse,which makes it possible to obtain a good X ray image in which contrastof the peripheral portions (edge portions), such as a cartilage tissueof human body, etc., are emphasized by employing the Talbotinterferometer method and the Talbot-Lau interferometer method, and toprovide a radiological image capturing system in which theabove-captured X ray image is processed.

Accordingly, at least one of the objects of the present invention can beattained by any one of the radiological image capturing apparatuses andthe radiological image capturing systems described as follows.

(1) According to a radiological image capturing apparatus reflecting anaspect of the present invention, the radiological image capturingapparatus, comprises: an X ray tube to emit X rays having an averageenergy in a range of 15-60 keV; a subject placing plate to place asubject thereon; a multi-slit element that is disposed at a positionlocated on an optical path of the X rays, emitted by the X ray tube, andthat has plural slits formed therein; a first diffraction grating todiffract the X rays penetrated through the subject, so as to yield aTalbot effect; a second diffraction grating to diffract the X raysdiffracted by the first diffraction grating; and an X-ray detector todetect the X rays diffracted by the second diffraction grating; whereinthe multi-slit element and the second diffraction grating are in contactwith each other; and wherein a first distance between the multi-slitelement and the first diffraction grating, a second distance between thefirst diffraction grating and the second diffraction grating, and a slitinterval distance of the multi-slit element are set at a value equal toor greater than 0.5 m, a value equal to or greater than 0.05 m and avalue equal to or greater than 2 μm, respectively.(2) According to another aspect of the present invention, theradiological image capturing apparatus, recited in item 1, furthercomprises: a control device that compares a Moiré stripe image, capturedbefore an actual operation of the radiological image capturing apparatusis commenced, with another Moiré stripe image captured after the actualoperation of the radiological image capturing apparatus is commenced, todetermine whether or not a distortion is generated in a diffractionmember of the first diffraction grating or the second diffractiongrating.(3) According to still another aspect of the present invention, in theradiological image capturing apparatus recited in item 1, the controldevice issues a warning notification corresponding to a result ofdetermining whether or not the distortion is generated.(4) According to still another aspect of the present invention, theradiological image capturing apparatus, recited in item 1, furthercomprises: a first temperature sensor to measure a first temperature ofthe first diffraction grating; a second temperature sensor to measure asecond temperature of the second diffraction grating; and a controldevice to determine whether or not at least one of the first temperatureand the second temperature, measured through the first temperaturesensor and/or the second temperature sensor, is equal to or greater thana reference temperature established in advance.(5) According to still another aspect of the present invention, in theradiological image capturing apparatus recited in item 4, the controldevice issues a warning notification corresponding to a result ofdetermining whether or not at least one of the first temperature and thesecond temperature is equal to or greater than the referencetemperature.(6) According to still another aspect of the present invention, in theradiological image capturing apparatus recited in item 1, the firstdiffraction grating, the second diffraction grating and the X-raydetector are made to rotate around a peripheral space of the subject, soas to continuously capture X ray images of the subject from variousdirections.(7) According to still another aspect of the present invention, in theradiological image capturing apparatus recited in item 1, the multi-slitelement is capable of entering into and withdrawing from the opticalpath of the X rays emitted by the X ray tube; and the radiological imagecapturing apparatus further comprising: a control device to control themulti-slit element to enter into and withdraw from the optical path.(8) According to still another aspect of the present invention, in theradiological image capturing apparatus recited in item 7, when themulti-slit element is disposed at the position located on the opticalpath, the control device sets the first distance between the multi-slitelement and the first diffraction grating at a value equal to or greaterthan 0.5 m, while, when the multi-slit element withdraws from theoptical path, the control device sets a third distance between the X raytube and the first diffraction grating at a value equal to or greaterthan 0.5 m and sets a focal point diameter of the X ray tube at a valueequal to or greater than 1 μm.(9) According to still another aspect of the present invention, in theradiological image capturing apparatus recited in item 7, the controldevice is configured to detect an abnormal shadow candidate from the Xray image captured, so as to change a Talbot-Lau interferometer methodto a Talbot interferometer method when detecting the abnormal shadowcandidate, as a method to be currently employed in the radiologicalimage capturing apparatus.(10) According to a radiological image capturing apparatus reflectingstill another aspect of the present invention, the radiological imagecapturing apparatus, comprises: an X ray tube to emit X rays having anaverage energy in a range of 15-60 keV; a subject placing plate to placea subject thereon; a multi-slit element that is disposed at a positionlocated on an optical path of the X rays, emitted by the X ray tube, andthat has plural slits formed therein; a first diffraction grating todiffract the X rays, so as to yield a Talbot effect; a seconddiffraction grating to diffract the X rays diffracted by the firstdiffraction grating and penetrated through the subject; and an X-raydetector to detect the X rays diffracted by the second diffractiongrating; wherein the multi-slit element and the second diffractiongrating are in contact with each other; and wherein a first distancebetween the multi-slit element and the first diffraction grating, asecond distance between the first diffraction grating and the seconddiffraction grating, and a slit interval distance of the multi-slitelement are set at a value equal to or greater than 0.5 m, a value equalto or greater than 0.05 m and a value equal to or greater than 2 μm,respectively.(11) According to a radiological image capturing system reflecting stillanother aspect of the present invention, the radiological imagecapturing system, comprises: a radiological image capturing apparatusthat is provided with: an X ray tube to emit X rays having an averageenergy in a range of 15-60 keV; a subject placing plate to place asubject thereon; a multi-slit element that is disposed at a positionlocated on an optical path of the X rays, emitted by the X ray tube, andthat has plural slits formed therein; a first diffraction grating todiffract the X rays penetrated through the subject, so as to yield aTalbot effect; a second diffraction grating to diffract the X raysdiffracted by the first diffraction grating; and an X-ray detector todetect the X rays diffracted by the second diffraction grating; whereinthe multi-slit element and the second diffraction grating are in contactwith each other; and wherein a first distance between the multi-slitelement and the first diffraction grating, a second distance between thefirst diffraction grating and the second diffraction grating, and a slitinterval distance of the multi-slit element are set at a value equal toor greater than 0.5 m, a value equal to or greater than 0.05 m and avalue equal to or greater than 2 μm, respectively; an image processingapparatus to apply various kinds of image processing to image datarepresenting an image captured by the radiological image capturingapparatus; and an image outputting apparatus to output the image basedon the image data processed by the image processing apparatus.(12) According to a radiological image capturing system reflecting stillanother aspect of the present invention, the radiological imagecapturing system, comprises: a radiological image capturing apparatusthat is provided with: an X ray tube to emit X rays having an averageenergy in a range of 15-60 keV; a subject placing plate to place asubject thereon; a multi-slit element that is disposed at a positionlocated on an optical path of the X rays, emitted by the X ray tube, andthat has plural slits formed therein; a first diffraction grating todiffract the X rays, so as to yield a Talbot effect; a seconddiffraction grating to diffract the X rays diffracted by the firstdiffraction grating and penetrated through the subject; and an X-raydetector to detect the X rays diffracted by the second diffractiongrating; wherein the multi-slit element and the second diffractiongrating are in contact with each other; and wherein a first distancebetween the multi-slit element and the first diffraction grating, asecond distance between the first diffraction grating and the seconddiffraction grating, and a slit interval distance of the multi-slitelement are set at a value equal to or greater than 0.5 m, a value equalto or greater than 0.05 m and a value equal to or greater than 2 μm,respectively; an image processing apparatus to apply various kinds ofimage processing to image data representing an image captured by theradiological image capturing apparatus; and an image outputtingapparatus to output the image based on the image data processed by theimage processing apparatus.(13) According to a radiological image capturing system reflecting stillanother aspect of the present invention, the radiological imagecapturing system, comprises: a radiological image capturing apparatusthat is provided with: an X ray tube to emit X rays having an averageenergy in a range of 15-60 keV; a subject placing plate to place asubject thereon; a multi-slit element that is disposed at a positionlocated on an optical path of the X rays, emitted by the X ray tube, andthat has plural slits formed therein; a first diffraction grating todiffract the X rays penetrated through the subject, so as to yield aTalbot effect; a second diffraction grating to diffract the X raysdiffracted by the first diffraction grating; and an X-ray detector todetect the X rays diffracted by the second diffraction grating; whereinthe multi-slit element and the second diffraction grating are in contactwith each other; and wherein a first distance between the multi-slitelement and the first diffraction grating, a second distance between thefirst diffraction grating and the second diffraction grating, and a slitinterval distance of the multi-slit element are set at a value equal toor greater than 0.5 m, a value equal to or greater than 0.05 m and avalue equal to or greater than 2 μm, respectively; and a diagnosisassistance apparatus to detect an abnormal shadow candidate from an Xray image captured by the radiological image capturing apparatus;wherein the multi-slit element is capable of entering into andwithdrawing from the optical path of the X rays emitted by the X raytube, and the radiological image capturing apparatus is further providedwith a control device to control the multi-slit element to enter intoand withdraw from the optical path; and wherein the control device isconfigured to detect an abnormal shadow candidate from the X ray imagecaptured, so as to change a Talbot-Lau interferometer method to a Talbotinterferometer method when the diagnosis assistance apparatus detectsthe abnormal shadow candidate, as a method to be currently employed inthe radiological image capturing apparatus.(14) According to a radiological image capturing system reflecting yetanother aspect of the present invention, the radiological imagecapturing system, comprises: a radiological image capturing apparatusthat is provided with: an X ray tube to emit X rays having an averageenergy in a range of 15-60 keV; a subject placing plate to place asubject thereon; a multi-slit element that is disposed at a positionlocated on an optical path of the X rays, emitted by the X ray tube, andthat has plural slits formed therein; a first diffraction grating todiffract the X rays, so as to yield a Talbot effect; a seconddiffraction grating to diffract the X rays diffracted by the firstdiffraction grating and penetrated through the subject; and an X-raydetector to detect the X rays diffracted by the second diffractiongrating; wherein the multi-slit element and the second diffractiongrating are in contact with each other; and wherein a first distancebetween the multi-slit element and the first diffraction grating, asecond distance between the first diffraction grating and the seconddiffraction grating, and a slit interval distance of the multi-slitelement are set at a value equal to or greater than 0.5 m, a value equalto or greater than 0.05 m and a value equal to or greater than 2 μm,respectively; and a diagnosis assistance apparatus to detect an abnormalshadow candidate from an X ray image captured by the radiological imagecapturing apparatus; wherein the multi-slit element is capable ofentering into and withdrawing from the optical path of the X raysemitted by the X ray tube, and the radiological image capturingapparatus is further provided with a control device to control themulti-slit element to enter into and withdraw from the optical path; andwherein the control device is configured to detect an abnormal shadowcandidate from the X ray image captured, so as to change a Talbot-Lauinterferometer method to a Talbot interferometer method when thediagnosis assistance apparatus detects the abnormal shadow candidate, asa method to be currently employed in the radiological image capturingapparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, withreference to the accompanying drawings which are meant to be exemplary,not limiting, and wherein like elements are numbered alike in severalFigures, in which:

FIG. 1 shows schematic diagram indicating an overall configuration of aradiological image capturing system, embodied in the present invention;

FIG. 2 shows a schematic diagram indicating an exemplary configurationof a radiological image capturing apparatus, embodied in the presentinvention;

FIG. 3 shows a schematic diagram indicating an internal configuration ofa radiological image capturing apparatus, shown in FIG. 2;

FIG. 4 shows a perspective view indicating a configuration of amulti-slit element;

FIG. 5 shows perspective views of a first diffraction grating, a seconddiffraction grating and temperature sensors;

FIG. 6 shows a block diagram indicating a controlling configuration of aradiological image capturing apparatus, embodied in the presentinvention;

FIG. 7 shows a perspective view of a main part for explainingpenetrating actions of X rays and Moiré stripes when a radiologicalimage capturing apparatus is used in a Talbot interferometer method;

FIG. 8 shows a perspective view of a main part for explainingpenetrating actions of X rays and Moiré stripes when a radiologicalimage capturing apparatus is used in a Talbot-Lau interferometer method;

FIG. 9 shows a cross sectional view at an I-I position shown in FIG. 7;

FIG. 10 shows a cross sectional view at an II-II position shown in FIG.7;

FIG. 11 shows a schematic diagram for explaining such a state that aself-image of a first diffraction grating, which is formed by X rayspassing through each of slits of a multi-slit element, is just in focuson a second diffraction grating;

FIG. 12 shows an explanatory schematic diagram for explaining apositional relationship between a X ray tube, a subject H, a firstdiffraction grating, a second diffraction grating and an X-ray detector,in a radiological image capturing apparatus employing the Talbotinterferometer method;

FIG. 13 shows an explanatory schematic diagram for explaining apositional relationship between a X ray tube, a multi-slit element, asubject H, a first diffraction grating, a second diffraction grating andan X-ray detector, in a radiological image capturing apparatus employingthe Talbot-Lau interferometer method; and

FIG. 14 shows a schematic diagram indicating an exemplary configurationof a radiological image capturing apparatus, which is configured so asto arrange a subject H at a position between a first diffraction gratingand a second diffraction grating.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, the radiological image capturing apparatusand the radiological image capturing system, both embodied in thepresent invention, will be detailed in the following. However, the scopeof the present invention is not limited to the examples indicated in thedrawings.

In the present embodiment, a radiological image capturing system 100 isconstituted by: a radiological image capturing apparatus 1 thatirradiates X rays, serving as radial rays, onto a subject so as togenerate radiological image data of the subject; an image processingapparatus 30 that applies various kinds of image processing to theradiological image data generated by the radiological image capturingapparatus 1; and an image outputting apparatus 50 that outputs aradiological image, etc., onto a display screen or a film, based onprocessed image data generated by applying the various kinds of imageprocessing to the radiological image data in the image processingapparatus 30. Each of the radiological image capturing apparatus 1, theimage processing apparatus 30 and the image outputting apparatus 50 iscoupled to a communication network N (hereinafter, referred to as anetwork N, for simplicity), such as a LAN (Local Area Network), etc.,for instance, through a switching hub, etc., (not shown in thedrawings).

In this connection, the scope of the configuration of the radiologicalimage capturing system 100 is not limited to the system exemplified inFIG. 1. For instance, it is also applicable that the radiological imagecapturing system is so constituted that the image processing apparatus30 and the image outputting apparatus 50 are integrated into a singleapparatus, so that the integrated single apparatus conducts both theimage processing operations and the radiological image outputtingoperation (onto the display screen or the film) based on the processedimage data.

As shown in FIG. 2 and FIG. 3, the radiological image capturingapparatus 1 is provided with a base frame 2 that is fixed on the floorsurface with bolts or the like and a supporting base member 3 that ismovable in both up and down directions relative to the base frame 2.Further, an image capturing main section 4 is supported by thesupporting base member 3 through a supporting shaft 5. The supportingshaft 5 is constituted by an outer supporting cylinder 5 a shaped in acylinder and an inner supporting shaft 5 b disposed inside the outersupporting cylinder 5 a, so as to make the outer supporting cylinder 5 arotatable in either a clockwise direction or a counterclockwisedirection around the inner supporting shaft 5 b, serving as the rotatingaxis.

The supporting base member 3 is provided with a driving device 6 fordriving its up-and-down movements and the rotational motion of thesupporting shaft 5, and the driving device 6 is provided with aconventional driving motor (not shown in the drawings). The imagecapturing main section 4 is fixed to the outer supporting cylinder 5 aso as to elevate or descend synchronized with the up-and-down movementsof the supporting base member 3 through the supporting shaft 5. Further,the image capturing main section 4 is rotated around the innersupporting shaft 5 b, serving as the rotating axis, by making the outersupporting cylinder 5 a rotate in either the clockwise direction or thecounterclockwise direction.

A supporting bar member 7, shaped in substantially a bar, is fixed inthe image capturing main section 4 in such a manner that the supportingbar member 7 can expand and contract in both up and down directions. AnX ray tube 8 that irradiates X rays onto a subject H is disposed at theupper section of the supporting bar member 7 in such a manner that the Xray tube 8 can freely elevate and descend. The X ray tube 8 is driven toelevate or descend by a position adjustment device 9, which is providedwith a conventional driving motor, etc. (not shown in the drawings), soas to adjust the position of the X ray tube 8. Further, a power source10 to supply electric power is coupled to the X ray tube 8 through thesupporting base member 3, the supporting shaft 5 and image capturingmain section 4. Still further, an aperture 8 a to adjust the X-rayirradiation field is disposed at an X-ray irradiation opening of the Xray tube 8 in such a manner that the aperture 8 a can be freely openedand closed, and the aperture 8 a elevates and descend with the X raytube 8.

A X ray tube that can irradiate X rays, having an average energy in arange of 15-60 keV, is employed as the X ray tube 8 abovementioned. Thisis because, when the average energy of the X rays to be irradiated, issmaller than 15 keV, since almost of all part of the irradiated X raysare absorbed into the subject, a dose of X ray exposure becomesextremely great, and accordingly, such the setting is not suitable forclinical use. On the other hand, when the average energy of the X raysto be irradiated, is greater than 60 keV, it has been impossible toacquire such the X-ray radiation image that has sufficient contrasts soas to clearly represent bones, soft tissue sections, etc., whichconstitute the human body, and therefore, there is a possibility thatthe acquired X-ray radiation image cannot be used for a medicaldiagnosis or the like.

It is preferable that, for instance, the Coolidge X-ray tube or therotation anode X-ray tube, which has been widely used in the actualmedical field, is employed as the X ray tube 8. On that occasion, when amolybdenum (Mo) material is employed for the target (anode) of the X-raytube, as widely employed in the breast image radiographing operation(mammography, in this case, a molybdenum filter, having a thickness of30 μm, is normally added), generally speaking, the X rays having theaverage energy of 15 keV are emitted from the X-ray tube at the timewhen a set voltage of 22 kVp is applied to the X-ray tube concerned,while the X rays having the average energy of 21 keV are emitted fromthe X-ray tube at the time when a set voltage of 39 kVp is applied tothe X-ray tube concerned. Further, when a tungsten (W) material isemployed for the target (anode) of the X-ray tube, as widely employed inthe normal radiographing operation, generally speaking, the X rayshaving the average energies of 22, 32, 47 and 60 keV are emitted fromthe X-ray tube at the time when set voltages of 30, 50, 100 and 150 kVpis applied to the X-ray tube concerned, respectively.

In the case of the radiological image capturing apparatus 1, embodied inthe present invention, in which not only operations for radiographingjoint disorders, which are represented by the rheumatic disease, butalso various kinds of other radiographing operations, such as a breastimage radiographing operation that should be capable of detecting amicro calcification from a breast, most of which is formed by a softtissue, an operation for radiographing a child body, almost bones ofwhich are cartilages, etc., are objects to be conducted, since thesharpness of the captured image can be improved due to the phasecontrast effect by irradiating the X rays, specifically having a lowX-ray energy (voltage to be applied to the X-ray tube concerned is setat a low voltage), among the X rays having various levels of the averageenergies, it is preferable that the average energy of the X rays to beirradiated is in a range of 15-32 keV. Further, considering the does ofradiation exposure, it is more preferable that the average energy of theX rays to be irradiated is in a range of 20-27 keV. This can be achievedby employing the tungsten (W) material for the target of the X-ray tubeconcerned.

The radiological image capturing apparatus 1 is so constituted that theTalbot interferometer method and the Talbot-Lau interferometer method,both detailed later, can be selectively changed to each other. When theradiological image capturing apparatus 1 is used as the Talbotinterferometer, the focal diameter of the X ray tube 8 is set at such avalue that is equal to or greater than 1 μm, so as to irradiate the Xrays having the average energy in the abovementioned range and toacquire a practical output intensity. In this connection, in order toacquire a sufficient X-ray intensity, it is preferable that the focaldiameter of the X ray tube 8 is set at a value being equal to or greaterthan 7 μm. Further, the X rays to be incident onto the first diffractiongrating, detailed later, should have a coherence property. From thepoint that the X rays to be employed has the average energy in a rangeof 15-60 keV, and from the other point that the upper limit of thelength of the radiographing apparatus is around 2 meters at the longestas detailed later, it is preferable that the focal diameter of the X raytube 8 is set at a value being equal to or smaller than 50 μm, in orderto posses the coherence property. Further, in order to improve thecoherence property and to acquire a clear image by effectively using theTalbot effect detailed later, it is more preferable that the focaldiameter of the X ray tube 8 is set at a value being equal to or smallerthan 30 μm.

Further, when the radiological image capturing apparatus 1 is used asthe Talbot-Lau interferometer, the X rays to be incident onto the firstdiffraction grating, detailed later, should have a coherence property,as well as the above, and it is preferable that the focal diameter ofthe X ray tube 8 is set at a smaller value, in order to posses thecoherence property. However, according to the present invention, sincethe X rays emitted by the X ray tube 8 are converted to multi (plural)radiant sources by employing a multi-slit element 11 detailed later, andin addition, the high power outputting capability is required for the Xray tube 8, it is not necessary to make the focal diameter of the X raytube 8 so small.

Accordingly, in the Talbot-Lau interferometer method embodied in thepresent invention, the focal diameter of the X ray tube 8 is set at avalue being equal to or greater than 10 μm. Concretely speaking, it ispreferable that the focal diameter of the X ray tube 8 is in a range of10-500 μm, and more preferable that the focal diameter of the X ray tube8 is set at a value being equal to or greater than 50 μm. Practically,the focal diameter is preferably set at a value being in a range of100-300 μm. In this connection, it is possible to measure the focaldiameter of the X ray tube 8 by employing the method established in “JISZ4704-1994, 7.4.1 FOCAL POINT TEST, (2.2) Slit Camera”. Further, anX-ray irradiation time (exposure time) for completing everyradiographing operation can be set at around several parts of onesecond, or two-three seconds at the longest.

In the present embodiment, a control device, detailed later, conducts anoperation for changing the focal diameter of the X ray tube 8 from oneto another by changing the angle of the target of the X ray tube.Various kinds of methods, such as a method for inclining the target, amethod for providing the target having two angles in advance andchanging the position of the target onto which the electron beam isirradiated, etc., can be employed for changing the angle of the targetof the X ray tube. Other than the above, it is also possible that thesystem is so constituted that, for instance, the focal diameter of the Xray tube 8 is changed from one to another by changing the area of theelectron beam to be irradiated onto the target, or plural X ray tubes,focal diameters of which are different from each other, are provided inthe system, so as to change the X ray tube 8 itself from one to anotherat the time of the changeover operation between the Talbotinterferometer method and Talbot-Lau interferometer method.

In this connection, it is preferable that the X ray tube 8 fulfills sucha condition that the half-value width of the wavelength distribution ofthe X rays to be irradiated is equal to or smaller than 0.1 times of thepeak wavelength of the X rays concerned. As far as the X ray tube 8fulfills such the condition as abovementioned, the scope of theapplicable X ray tube is not limited to the Coolidge X-ray tube or therotation anode X-ray tube aforementioned, and the micro-focus X raysource or the like may be applicable as the X ray tube 8.

As shown in FIG. 3, the multi-slit element 11 is disposed at a lowerside of the X ray tube 8. When the radiological image capturingapparatus 1 is used as the Talbot-Lau interferometer method, themulti-slit element 11 is inserted into the optical path of the X raysemitted from the X ray tube 8, while, when the radiological imagecapturing apparatus 1 is used as the Talbot interferometer method, themulti-slit element 11 is made to withdraw from the optical pathconcerned.

As shown in FIG. 4, the multi-slit element 11 is constituted by pluralthin plates, which are arranged so as to make a plurality of slits 111line up in parallel to each other. Each of the plural thin plates ismade of such a material that can shield the X rays (X ray absorbingcapability is great), for instance, a lead, a tungsten, etc. Further, anaperture width of each of the slits 111 (namely, a slit width, so tospeak) is set at a value in a range of 1-50 μm. In order to effectivelyutilize the Talbot effect and to acquire a sufficient amount of X rays,it is preferable that the slit width is formed at a value in a range ofaround 7-30 μm. Accordingly, the X rays that are incident onto the firstdiffraction grating, detailed later, are converted into the multi(plural) radiant sources while having the coherency property. In thisconnection, a space distance d₀ between the slits 111 of the multi-slitelement 11 will be detailed later on.

Further, the slits 111 of the multi-slit element 11 are formed onlywithin an area of the X-ray irradiation field of the X rays emitted fromthe X ray tube 8. As shown in FIG. 3, the multi-slit element 11 issupported by the supporting bar member 7 through a supporting member 112in such a manner that the multi-slit element 11 can freely elevate anddescend, and a position adjusting device 9 moves it upward or downwardalong the supporting bar member 7 so as to adjust the position of themulti-slit element 11.

In the present embodiment, the multi-slit element 11 is mounted onto thesupporting bar member 7 in such a manner that the multi-slit element 11is made to rotate around the axis of the supporting bar member 7 by thedriving action of the position adjusting device 9. Accordingly, when theradiological image capturing apparatus 1 is used as the Talbotinterferometer, the multi-slit element 11 is made to rotate around theaxis of the supporting bar member 7 so as to withdraw from the opticalpath aforementioned. On the other hand, when the radiological imagecapturing apparatus 1 is used as the Talbot-Lau interferometer, themulti-slit element 11 is made to rotate around the axis of thesupporting bar member 7 so as to insert it into the optical pathaforementioned.

In this connection, it is also applicable that another driving device isemployed for conducting the abovementioned rotating action or theradiological image capturing apparatus 1 is so constituted that theabovementioned rotating action can be manually achieved. For instance,other than the above, it is also applicable that the coupling portionbetween the multi-slit element 11 and the supporting bar member 7 isconfigured as being capable of freely expanded and contracted, so thatthe multi-slit element 11 is inserted into or is made to withdraw fromthe optical path of the X rays by moving it toward the supporting barmember 7 or in a direction apart from the supporting bar member 7.

The multi-slit element 11 is disposed in such a manner that the extendeddirections of the slits 111 are parallel to those of diffraction members152 of a first diffraction grating 15 detailed later. Further, as shownin FIG. 2, since the farther the X rays irradiated from the X ray tube 8depart from the X ray tube 8, the wider the irradiation area of the Xrays becomes, if the multi-slit element 11 is disposed at a positionbeing far apart from the X ray tube 8, the area of the multi-slitelement 11 should be widened, and possibly causes a physicalinterference with the subject H. In order to avoid the aboveinconveniences, it is preferable that the multi-slit element 11 isdisposed at such a position that is apart from the focal point of the Xray tube 8 with a distance in a range of around 1-10 cm. In thisconnection, hereinafter, precisely speaking in the present invention,the distance between the X ray tube 8 and another member represents thedistance between the focal point of the X ray tube 8 and another member.

A subject placing plate 12, on which the subject H is to be placed, isdisposed at a position located below the X ray tube 8, in such a mannerthat the subject placing plate 12 is extended from the inner supportingshaft 5 b of the supporting shaft 5 substantially in parallel to thefloor surface. The subject placing plate 12 and the inner supportingshaft 5 b are fixed neither to the image capturing main section 4 nor tothe supporting bar member 7. Therefore, even if the image capturing mainsection 4 is driven to rotate clockwise or counterclockwise by therotating action of the outer supporting cylinder 5 a of the supportingshaft 5, the subject placing plate 12 does not rotate in conjunctionwith the rotating action of the outer supporting cylinder 5 a.

The subject placing plate 12 can also rotate around the inner supportingshaft 5 b, etc., as needed, and further, a pressing plate 13 presses thesubject H onto the subject placing plate 12 so as to fix the subject Hthereon, as needed. The pressing plate 13 is supported by the subjectplacing plate 12 through a supporting member (not shown in thedrawings). It is applicable that the pressing plate 13 is made to moveeither automatically or manually.

As mentioned in the above, the subject placing plate 12 elevates anddescends in conjunction with the up-and-down movements of the supportingbase member 3 through the supporting shaft 5, for instance, so that theposition of the subject placing plate 12 is adjusted at such a positionthat a patient can take an easy stance (natural posture) while puttinghis arm, serving as the subject H, on the subject placing plate 12.Further, a protector 14, which is extended in substantially a verticaldirection, is mounted to the lower surface of the subject placing plate12, so that the patient can take his position at the radiographingposition without hitting his leg to a structure equipped under thesubject placing plate 12 and without receiving X-ray exposure. In thisconnection, the pressing plate 13 and the protector 14 are not necessaryindispensable structural elements, but it is applicable that the systemcan be configured without employing them.

The first diffraction grating 15 is disposed at a central section of thesupporting bar member 7, located below the subject placing plate 12, insuch a manner that the first diffraction grating 15 is made to freelyelevate and descend, and a second diffraction grating 16 is disposed ata lower section of the supporting bar member 7, in such a manner thatthe second diffraction grating 16 is made to freely elevate and descend.The first diffraction grating 15 and the second diffraction grating 16are held so as to arrange them in parallel to each other. The structuresof the first diffraction grating 15 and the second diffraction grating16, and positional relationships between an X-ray detector 17, detailedlater, and them will be detailed later on.

As aforementioned, since the X rays irradiated from the X ray tube 8 areconverted to the multi radiant sources by the multi-slit element 11, itis possible to regard the multi-slit element 11 as a radiant source.Further, it is necessary to appropriately adjust the distance betweenthe first diffraction grating 15 and the radiant source. Accordingly,when the radiological image capturing apparatus 1 is used as the Talbotinterferometer in which the first diffraction grating 15 is made towithdraw from the optical path of the X rays, the position adjustingdevice 9 makes the first diffraction grating 15 elevate and descend withrespect to the supporting bar member 7 so as to adjust a distance Lbetween the X ray tube 8 and the first diffraction grating 15. While,when the radiological image capturing apparatus 1 is used as theTalbot-Lau interferometer in which the first diffraction grating 15 isinserted into the optical path of the X rays, since the X raysirradiated from the X ray tube 8 are converted to the multi radiantsources by the multi-slit element 11, it is possible to regard themulti-slit element 11 as the radiant source, as aforementioned.Accordingly, the position adjusting device 9 makes the first diffractiongrating 15 elevate and descend with respect to the supporting bar member7, so as to adjust a distance L between the multi-slit element 11,serving as the radiant source, and the first diffraction grating 15.

Further, the position adjusting device 9 makes the second diffractiongrating 16 elevate and descend with respect to the supporting bar member7, so as to adjust a distance Z₁ between the first diffraction grating15 and the second diffraction grating 16. In this connection, in thepresent embodiment, the position adjusting device 9 makes each of thefirst diffraction grating 15 and the second diffraction grating 16elevate and descend independently from each other.

Further, for instance as shown in FIG. 5, a first temperature sensor 15a and a second temperature sensor 16 a are mounted on the firstdiffraction grating 15 and the second diffraction grating 16 anddisposed at such positions that cannot be captured as X-ray images,respectively. In this connection, for instance, it is applicable thatsheets, which are made of material having a good thermal conductivityand does not impede the X-ray radiographing operation, are adhered ontothe first diffraction grating 15 and the second diffraction grating 16,respectively, so as to keep the temperature uniform within the surfaceof each of them. Further, for instance, it is also applicable thatPeltier elements, which are capable of conducting heating and coolingoperations by controlling the direction and amplitude of electriccurrents flowing through them, are installed into the first diffractiongrating 15 and the second diffraction grating 16, respectively, so as tomake it possible to conduct the heating and cooling operations of them.

As shown in FIG. 2 and FIG. 3, a detector supporting plate 18 forsupporting an X-ray detector 17 is supported at a lower section of thesecond diffraction grating 16, in such a manner that the X-ray detector17 is made to freely elevate and descend with respect to the supportingbar member 7. Further, the position adjusting device 9 makes thedetector supporting plate 18 elevate and descend independently from thefirst diffraction grating 15, etc., so as to adjust the positionthereof.

The X-ray detector 17 is supported on the detector supporting plate 18so as to oppose to the X ray tube 8. Although the X-ray detector 17 andthe second diffraction grating 16 are depicted in the schematic diagramsshown in FIG. 2, FIG. 3, etc., in such a manner that some distance Z2exists between them, in order to indicate that the X-ray detector 17 andthe second diffraction grating 16 are separate elements, in reality, itis preferable that the X-ray detector 17 and the second diffractiongrating 16 are disposed in such a state that both of them are in contactwith each other. This is because, the farther the X-ray detector 17departs from the second diffraction grating 16, the more the Moiréfringes become blurred. In other words, both of them are arranged so asto make the distance Z2 equal to substantially zero. In this connection,it is also applicable that the X-ray detector 17 and the seconddiffraction grating 16 are integrally structured as a single element.Further, in order to prevent a part of the human body, residing belowthe X-ray detector 17, from the X-ray exposure caused by the X raysemitted by the X ray tube 8, various kinds of radiation shieldingmembers (not shown in the drawings) are disposed at the lower side ofX-ray detector 17 and installed into the detector supporting plate 18,etc.

The X-ray detector 17 is constituted by a panel, a detector controllingsection, etc. (not shown in the drawings), which are coupled to eachother through a bus. Further, the X-ray detector 17 detects an amount ofX rays penetrated through the subject H after emitted from the X raytube 8, so as to output X-ray image data, representing the detectedamount of X rays, to the image processing apparatus 30 through a networkN.

It is preferable that a detector that employs any one of a FPD (FlatPanel Detector), a CR (Computed Radiography) and CCD (Charge CoupledDevice), each of which output the amount of X rays as the digitalinformation for every pixel, is used as the X-ray detector 17. Amongthem, the FPD, which is superior to the others as the two dimensionalimage sensor, is specifically preferable for this purpose. The overallsize of the panel is selected as needed.

A distance L_(total) between the X-ray detector 17 and the X ray tube 8or the multi-slit element 11, serving as the radiant source, is set atsuch a value that is equal to or greater than 0.5 m. Further,considering the fact that the radiological image capturing apparatus 1is used in a room environment and accuracy, strength, etc. of theradiological image capturing apparatus 1, the upper limit of thedistance L_(total) is set at around 2 m.

A control device 20, indicated in the schematic diagram shown in FIG. 6,conducts various kinds of setting operations and controlling operationsfor controlling actions to be conducted in the radiological imagecapturing apparatus 1. The control device 20 is provided with a computerconstituted by a CPU (Central Processing Unit), a ROM (Read OnlyMemory), a RAM (Random Access Memory), etc., which are coupled to eachother through a bus.

Although it is possible to install the control device 20 into the sameroom in which the radiological image capturing apparatus 1 is alreadyinstalled, in the present embodiment, the control device 20 isconstituted by employing a computer that is provided in the imageprocessing apparatus 30 coupled to the radiological image capturingapparatus 1 through the network N. In other words, the control device 20and the image processing apparatus 30 are constituted by employing thesame computer. In this connection, it is also applicable that thecontrol device 20 is constituted by employing another computer, which isequipped separately from the image processing apparatus 30 and which iscoupled to the control device 20 through the network N.

As shown in FIG. 6, the control device 20 is coupled to the X ray tube8, the power source 10, the driving device 6, the position adjustingdevice 9, the first temperature sensor 15 a and the second diffractiongrating 16, which are described in the foregoing. Other than the above,the control device 20 is also coupled to a radiation amount detectingdevice 21 to detect an amount of irradiated X rays, an operating device22 that is provided with an input device 22 a and a display device 22 b,etc.

A controlling program for controlling various kinds of sections includedin the radiological image capturing apparatus 1 and various kinds ofprocessing programs are stored in a storage section of the controldevice 20, which includes the ROM, etc. Based on information inputted bythe operator from the input device 22 a, such as a keyboard, a mouse, acontroller, etc., the control device 20 reads out the controllingprogram and the various kinds of processing programs from the storagesection, so as to totally control operations to be conducted in thevarious kinds of sections included in the radiological image capturingapparatus 1, while making the display device 22 b, such as a CRTdisplay, a LCD (Liquid Crystal Display), etc., display contents ofcurrent controlling actions thereon.

For instance, when the operator inputs information for selecting any oneof the Talbot interferometer method or Talbot-Lau interferometer methodas a method to be currently employed in the radiological image capturingapparatus 1, and other information for setting the tube voltage to becurrently applied for the X ray tube 8 as aforementioned, from the inputdevice 22 a, the average energy of the X rays to be irradiated from theX ray tube 8 is determined, and further, the distance L between the Xray tube 8 and the first diffraction grating 15 or the other distance Lbetween the multi-slit element 11 serving as the radiant source and thefirst diffraction grating 15, and the distance Z₁ between the firstdiffraction grating 15 and the second diffraction grating 16 are alsodetermined. Further, when the second diffraction grating 16 and theX-ray detector 17 are made to tightly contact with each other asaforementioned, assuming that the distance between the X ray tube 8 andthe subject placing plate 12 is established as R1, and the otherdistance between the subject placing plate 12 and the X-ray detector 17is established as R2, with respect to the schematic diagram shown inFIG. 2, the magnification factor of the subject H is determined by thefollowing Equation, depending on the position of the subject placingplate 12.(magnification factor)=(R1+R2)/R1

Accordingly, in the present embodiment, when the operator inputs theselected method to be currently employed, the tube voltage of the X raytube 8, the distance L, the distance Z₁, etc., through the input device22 a, the control device 20 makes the position adjusting device 9 drivevarious kinds of sections, based on the inputted information, so as toconduct the operations for adjusting the positions of the X ray tube 8,the multi-slit element 11, the first diffraction grating 15, the seconddiffraction grating 16 and the X-ray detector 17. With respect to themulti-slit element 11, other than the position adjusting operationabovementioned, corresponding to the selected method currentlyestablished in the apparatus, the multi-slit element 11 is rotatedaround the axis of the supporting bar member 7 by the driving action ofthe position adjusting device 9 so as to insert it into the optical pathof the X rays (in the case of the Talbot-Lau interferometer method), orto make it withdraw from the optical path (in the case of the Talbotinterferometer method).

Successively, while maintaining the positional relationships of them,the positional adjusting operations are conducted by making the subjectplacing plate 12 elevate and descend in conjunction with the up and downmovements of the supporting base member 3, so that the subject personcan take a posture of being hardly fatigued.

In this connection, since the positional relationships should beadjusted so that the subject placing plate 12 and the first diffractiongrating 15 are not in contact with each other, certain limitations areapplied to the distances R1 and R2 aforementioned, and accordingly, asettable range of the magnification factor (=(R1+R2)/R1) is alsolimited. Accordingly, it is applicable that the radiological imagecapturing apparatus 1 is so constituted that the settable range of themagnification factor is displayed on the display device 22 b at the timewhen the selected method to be currently employed, the tube voltage ofthe X ray tube 8, the distance L, the distance Z₁ and the magnificationfactor are inputted.

Further, it is also applicable that the radiological image capturingapparatus 1 is so constituted that an LUT (Look Up Table), in which thedistances L and Z₁ being appropriate for the apparatus method and thetube voltage of the X ray tube 8 to be employed are stored, is providedin advance, so as to automatically set the distance L and the distanceZ₁ at the time when the selected method to be currently employed and thetube voltage of the X ray tube 8 are inputted. In this case, when theselected method to be currently employed and the tube voltage of the Xray tube 8 are inputted, the operations for adjusting the positions ofthe X ray tube 8, the first diffraction grating 15, the seconddiffraction grating 16 and the X-ray detector 17 are automaticallyimplemented, and further, when the magnification factor is inputted, theoperations for adjusting the positional relationships between thesubject placing plate 12 and them is implemented, corresponding to theabove-inputted magnification factor.

Still further, although the radiological image capturing apparatus 1embodied in the present invention is so constituted that, when theTalbot-Lau interferometer method is employed, the distance between themulti-slit element 11 disposed below the X ray tube 8 and the X ray tube8 is set at a predetermined distance value, it is also applicable thatthe abovementioned distance is set at another value by inputting it atthe same time when inputting the apparatus method and the tube voltageof the X ray tube 8 to be currently established in the apparatus, and/oran LUT for establishing a distance value, being optimum for theapparatus method and the tube voltage of the X ray tube 8 to becurrently employed, is provided in advance.

Still further, as aforementioned, when any one of the Talbotinterferometer method or the Talbot-Lau interferometer method isinputted as the selected apparatus method and the tube voltage of the Xray tube 8 is established, the control device 20 conducts the operationfor changing the diameter of focal point of the X ray tube 8corresponding to the selected apparatus method.

As abovementioned, the control device 20 activates the driving device 6to rotate the supporting shaft 5 clockwise or counterclockwise, as shownin FIG. 3, so that the image capturing main section 4 is rotated aroundthe subject H so as to adjust the radial-ray irradiation angle.

Further, when the radiological image capturing apparatus 1 is activated,the control device 20 irradiates the X rays emitted from the X ray tube8 onto the subject H according to the electric power supplied from thepower source 10 (in the case of the Talbot-Lau interferometer method,the X rays emitted from the multi radiant sources generated by themulti-slit element 11 are irradiated onto the subject H). Then, at thetime when an amount of X rays detected by the radiation amount detectingdevice 21 reaches the predetermined amount of X rays, established inadvance, the control device 20 stops the electric power currentlysupplied to the X ray tube 8 from the power source 10 so as todeactivates the X ray irradiating action. In this connection, theconditions for irradiating the X rays are established as needed byconsidering factors other than the amount of X rays detected by theradiation amount detecting device 21, namely, by taking a kind of theX-ray detector 17, etc. into account.

According to the present embodiment, since the control device 20activates the driving device 6 to rotate the supporting shaft 5, so thatthe image capturing main section 4 is rotated around the subject H, soas to rotate the X ray tube 8, the first diffraction grating 15, thesecond diffraction grating 16 and the X-ray detector 17 (in the case ofthe Talbot-Lau interferometer method, the multi-slit element 11 isfurther added) around the subject H, it is possible to continuouslycapture X ray images by irradiating the X rays onto the subject H fromplural directions. In this connection, the rotation amount of the imagecapturing main section 4 and an image capturing timing (corresponding toa rotated angle, at every which the X ray images are captured) areestablished by inputting them from the input device 22 a.

Further, the control device 20 determines whether or not temperatures ofthe first diffraction grating 15 and the second diffraction grating 16,which are measured by the first temperature sensor 15 a and the secondtemperature sensor 16 a, respectively, are equal to or greater than thepredetermined temperature established in advance. In the presentembodiment, when at least one of the temperatures of the firstdiffraction grating 15 and the second diffraction grating 16 becomesequal to or greater than the predetermined temperature established inadvance, a warning operation is conducted. The warning operation isachieved in such a manner that the control device 20 controls thedisplay device 22 b to display a kind of visual warning message thereonor to issue a kind of audible warning notification therefrom.

In this connection, in the case that the Peltier elements, which arecapable of conducting heating and cooling operations by controlling thedirections and amplitudes of electric currents flowing through them, areinstalled into the first diffraction grating 15 and the seconddiffraction grating 16, respectively, as aforementioned, when thetemperatures of the first diffraction grating 15 and the seconddiffraction grating 16, which are measured by the first temperaturesensor 15 a and the second temperature sensor 16 a, are increase ordecrease, it is possible to activate the Peltier elements so as tocontrol the temperatures of the first diffraction grating 15 and thesecond diffraction grating 16 to be kept within a predeterminedtemperature range.

Further, as detailed later, the radiological image capturing apparatus 1embodied in the present invention is so constituted that the controldevice 20 can determine whether or not a distortion due to thetemperature change or another distortion due to the change over time hasgenerated on the first diffraction grating 15 or the second diffractiongrating 16, based on an image of the Moiré fringes detected in such astate that the subject H is not placed on the subject placing plate 12(refer to Moiré fringes M indicated in the schematic diagram shown inFIG. 7, detailed later).

Concretely speaking, at the time stage when the radiological imagecapturing apparatus 1 is installed into a certain room after shippedfrom a factory, or when the first diffraction grating 15 and/or thesecond diffraction grating 16 are/is replaced with a new one, thecontrol device 20 stores an image of the Moiré fringes, which iscaptured in the state that the subject H is not placed on the subjectplacing plate 12 before the apparatus is put in its actual operation,into the storage section including a RAM, etc. After that, at the nexttime stage when a predetermined condition established in advance, suchas a condition that the operating time of the radiological imagecapturing apparatus 1, established in advance, has elapsed, a conditionthat a number of X ray irradiation times has reached to a predeterminednumber of times, etc., is fulfilled, the control device 20 newlyconducts the operation for capturing an image of the Moiré fringes inthe state that the subject H is not placed on the subject placing plate12. Otherwise, it is also applicable that the apparatus is soconstituted that the control device 20 periodically conducts theoperation for capturing an image of the Moiré fringes.

Successively, the control device 20 reads out the image of the Moiréfringes, captured and stored before the apparatus is put in its actualoperation, from the storage section, to compare it with the other imageof the Moiré fringes currently captured at this time. As a result of theabovementioned comparison, when the currently-captured image of theMoiré fringes fulfills at least one of the conditions that: an intervalof the Moiré fringes in the currently-captured image is expanded orreduced at a value equal to or greater than a predetermined value,compared to that in the image of the Moiré fringes captured and storedbefore the apparatus is put in its actual operation; a part of or all ofthe Moiré fringes are curved; a difference between a maximum part and aminimum part of detected amount of the irradiated X rays among the Moiréfringes is expanded or reduced at a value equal to or greater than apredetermined value; etc., the control device 20 determines that adistortion (deformation) has generated in the diffraction member(s)(grating) of the first diffraction grating 15 and/or the seconddiffraction grating 16. In this connection, it is applicable that theabovementioned operation is conducted in any one of the Talbotinterferometer method and the Talbot-Lau interferometer method, or inboth methods.

When determining that a distortion (deformation) has generated in thediffraction member(s) of the first diffraction grating 15 and/or thesecond diffraction grating 16 as abovementioned, the control device 20controls the display device 22 b to display a kind of visual warningmessage thereon or to issue a kind of audible warning notificationtherefrom.

Further, in the present embodiment, the apparatus is so constituted thatthe control device 20 detects an abnormal shadow candidate from thecaptured X-ray image. Further, the apparatus is so constituted that,when detecting the abnormal shadow candidate, the control device 20changes the apparatus method from the Talbot-Lau interferometer methodto the Talbot interferometer so as to capture the abnormal shadowcandidate being sharper than ever.

The operation for detecting the abnormal shadow candidate from thecaptured X-ray image can be conducted by employing, for instance, thetechnology of the medical image diagnosis assisting system, set forth inTokkai 2005-102936, which has been previously submitted by the applicantof the present invention. In this system, an image analysis processingis applied to the medical image, such as an X-ray image, etc., so as toextract its featuring amount, and then, based on the extracted featuringamount, an abnormal shadow candidate is detected from the imageconcerned.

In this connection, it is applicable that the system is so constitutedthat the abovementioned apparatus that detects the abnormal shadowcandidate from the X-ray image, captured by the radiological imagecapturing apparatus 1, is installed as the diagnosis assisting apparatus(not shown in the drawings) separately from the radiological imagecapturing apparatus 1, and is coupled to the radiological imagecapturing apparatus 1, etc. through the network N, so as to provide itwithin the radiological image capturing system 100.

For instance, it is also applicable that the system is so constitutedthat, when the diagnosis assisting apparatus detects an abnormal shadowcandidate and transmits information in regard to the detected abnormalshadow candidate, the control device 20 of the radiological imagecapturing apparatus 1 changes the method to be employed in theradiological image capturing apparatus 1 from the Talbot-Lauinterferometer method to the Talbot interferometer method, based on theinformation sent from the diagnosis assisting apparatus.

As shown in FIG. 1, the image processing apparatus 30 and the imageoutputting apparatus 50 are coupled to the radiological image capturingapparatus 1 through the network N. The image outputting apparatus 50includes: a display device, such as a CRT display, a LCD (Liquid CrystalDisplay), etc.; a developing device for outputting an image onto a film;etc.

Receiving X-ray image data for every captured image sent from the X-raydetector 17 of the radiological image capturing apparatus 1 through thenetwork N, the image processing apparatus 30 temporarily stores thereceived X-ray image data into a storage section (not shown in thedrawings). In this connection, at least one of an HDD (Hard Disc Drive)serving as a high-speed accessible mass memory, an HDD Array, such as aRAID (Redundant Array of Independent Disks), etc., a silicone disc, etc.can be employed as the storage section.

Further, the image processing apparatus 30 makes the radiological imagecapturing apparatus 1 capture an image of the Moiré fringes, and then,transmit X-ray image data of the image, so as to store the X-ray imagedata into storage section. This X-ray image data is temporarilyestablished as the reference X-ray image data. After that, when theradiological image capturing apparatus 1 commences the operation forcapturing an X-ray image of the subject H, the image processingapparatus 30 corrects the transmitted X-ray image data representing theimage that is captured by the radiological image capturing apparatus 1in a state that the subject H is present, based on the reference X-rayimage data.

The correcting operation is conducted with respect to, for instance, apositional deviation on the image, sensitivity unevenness (namely,non-uniformity in the signal values detected by the detector), etc.Concretely speaking, when it is recognized in advance from the referenceX-ray image data that a positional deviation is generated in a fixedpixel area on the image, it is possible to correct the positionaldeviation by conducting such the correcting operation that turns thefixed pixel area, existing in the image represented by the transmittedX-ray image data, back to the original position by an amount of thepositional deviation. Further, by dividing the X-ray image data, thepositional deviation of which has been corrected, by the reference X-rayimage data, for every pixel, it is possible to acquire an X-ray imagehaving no sensitivity non-uniformity to be caused by the existence ofthe diffraction grating. The image processing apparatus 30 also storesthe above-processed X-ray image data into the storage section.

Still further, it is possible for the image processing apparatus 30 notonly to convert the X-ray image (the image of the Moiré fringes)detected by the X-ray detector 17 to a distribution image of angles atwhich the X rays are curved by the refraction effect caused by thesubject H (phase shift differential image), but also to obtain such animage that represents the phase sift itself, acquired by integrating thephase shift differential image. The well-known methods, such as themethod set forth in the International Publication 2004/058070, etc., areemployed for the conversion processing and the image acquisitionprocessing, both abovementioned.

Yet further, in the present embodiment, when receiving plural X-rayimage data sets, which represent a plurality of X-ray imagescontinuously captured by changing the direction for radiographing thesubject H and are sent from the radiological image capturing apparatus1, the image processing apparatus 30 creates a three dimensional imageof the subject H, based on the above-received plural X-ray image datasets. The image outputting apparatus 50 displays the createdthree-dimensional image on the LCD, etc., or outputs it onto a film,etc., so as to output the three dimensional image created in the above.In this connection, a certain well-known method can be employed as themethod for creating the three dimensional image from the plurality oftwo-dimensional images acquired by capturing the subject H from thevarious directions.

In this connection, it is also possible to further apply another kind ofprocessing to the plurality of two-dimensional images and/or the threedimensional image, which are/is acquired through the abovementionedprocesses. For instance, it becomes possible to acquire such the image,etc., that is displayed on the screen or outputted on the film, in sucha manner that the brightness of the image, in which the concernedcartilage section is represented with the deep color in contrast to thepale color of the background, is reversed, or in such a manner that theconsiderably changed portion, compared to the standard model of thecartilage section, is colored, etc. Further, when a manifestation of therheumatic disease emerges on the finger, it becomes possible to observethe diseased part as if it were a moving image, by acquiring a pluralityof three-dimensional images in which the bending angles of the fingerjoints are varied in various kinds of directions.

In this connection, it is applicable that the abovementioned operationsare implemented in any one of the Talbot interferometer method and theTalbot-Lau interferometer method, or in both of them.

Next, the Talbot-Lau interferometer to be configured in the radiologicalimage capturing apparatus 1, embodied in the present invention, will bedetailed in the following. Further, the functions of the radiologicalimage capturing apparatus 1 will be detailed in the following, inconjunction with the explanations of the configurations of themulti-slit element 11, the first diffraction grating 15 and the seconddiffraction grating 16, and the explanations of the positionalrelationships between the X-ray detector 17 and them.

As shown in FIG. 7 and FIG. 8, in the present embodiment, the X raysirradiated from the X ray tube 8 penetrate through the multi-slitelement 11 in the case of the schematic diagram shown in FIG. 8, andsuccessively penetrate through the subject H, and then, penetratethrough the first diffraction grating 15 and the second diffractiongrating 16, and finally, are incident onto the X-ray detector 17. Asshown in FIG. 7, the Talbot interferometer is constituted by the X raytube 8, the first diffraction grating 15 and the second diffractiongrating 16, while, as shown in FIG. 8, the Talbot-Lau interferometer isconstituted by the X ray tube 8, the multi-slit element 11, the firstdiffraction grating 15 and the second diffraction grating 16.

FIG. 9 shows a cross sectional schematic diagram at the I-I crosssection indicated in the schematic diagrams shown in FIG. 7 and FIG. 8.As shown in FIG. 7 through FIG. 9, the first diffraction grating 15 isprovided with a substrate 151 and a plurality of the diffraction members152 that are arranged on the substrate 151, so as to yield a Talboteffect, detailed later, by diffracting the X rays that penetrate throughthe subject placing plate 12 and the subject H, held by the subjectplacing plate 12, and are irradiated thereon. The substrate 151 is madeof, for instance, a glass material or the like. In this connection, asurface of the substrate 151, on which the diffraction members 152 arearranged, is referred to as a diffraction grating surface 153.

Each of the diffraction members 152 is such a linear member that isextended in a direction orthogonal to the irradiation direction of the Xrays irradiated from the X ray tube 8, namely, for instance, that isextended in a up-down direction of the schematic diagrams shown in FIG.7 and FIG. 8. The thicknesses of the diffraction members 152 aresubstantially the same, for instance, each of them is formed in a rangeof 10-50 μm.

Further, as shown in FIG. 9, an interval distance d₁, being one ofrelative distances between the plural diffraction members 152, is set ata fixed value, and the relative distances between the diffractionmembers 152 are substantially the same. The interval distance d₁ isformed at a value in a range of around 3-10 μm. The interval distance d₁is also referred to as a grating period or a grating interval. In thisconnection, both the range of the interval distance d₁ in the pluraldiffraction members 152 and the other range of the width of each of thediffraction members 152 are not limited specifically. It is applicablethat the diffraction members 152 are formed in such a manner that theinterval distance between the diffraction members and the width of eachof the diffraction members are either the same as each other ordifferent from each other.

It is preferable that a material to be employed for structuring thediffraction members 152 is superior in the X rays absorbing property,and, for instance, a metallic material, such as a gold, a silver, aplatinum, etc., can be employed for this purpose. The diffractionmembers 152 are formed on the substrate 151, for instance, by plating orvapor-depositing the abovementioned metal thereon. The diffractionmembers 152 is such a member that changes the phase velocity of the Xrays irradiated onto the diffraction members 152, and it is preferablethat the diffraction members 152 is such a member that structures, socalled, the phase-type diffraction grating, which yields a phasemodulation at an angle in a range of about 80°-100°, preferably at 90°.The X rays are not necessary a single color, but it is applicable thatthe X rays have such an energy width (namely, a wavelength spectralwidth) that fulfils the abovementioned conditions.

FIG. 10 shows a cross sectional schematic diagram at the II-II crosssection indicated in the schematic diagrams shown in FIG. 7 and FIG. 8.As shown in FIG. 7, FIG. 8 and FIG. 10, the second diffraction grating16 is provided with a substrate 161 and a plurality of diffractionmembers 162 in the same manner as those of the first diffraction grating15. In this connection, a surface of the substrate 161, on which thediffraction members 162 are arranged, is referred to as a diffractiongrating surface 163.

Wherein, an interval distance d₂, being one of relative distancesbetween the plural diffraction members 162, is set at such a value thatthe ratio of the distance (L+Z₁) from the X ray tube 8 to the seconddiffraction grating 16 and the interval distance d₂ is substantiallyequal to the other ratio of the distance L from the X ray tube 8 to thefirst diffraction grating 15 and the interval distance d₁. In thisconnection, for instance, it is also possible to set the intervaldistance d₂, being one of relative distances between the pluraldiffraction members 162 of the second diffraction grating 16, at such avalue that is substantially the same as the interval distance d₁, beingone of relative distances between the plural diffraction members 152 ofthe first diffraction grating 15. Further, the width of each of thediffraction members 162 of the second diffraction grating 16 issubstantially the same as the width of each of the diffraction members152 of the first diffraction grating 15.

As detailed later, the second diffraction grating 16 is disposed in sucha state that the extended direction of the diffraction members 162 isrotated relative to the other extended direction of diffraction members152 of the first diffraction grating 15 by a minute angle θ, so as toform an image contrast by diffracting the X rays previously diffractedby the first diffraction grating 15. Although it is desirable that thesecond diffraction grating 16 is an amplitude-type diffraction gratingin which the diffraction members 162 are made to be thicker than ever,it is also possible to employ such a structure that is similar to thatof the first diffraction grating 15.

Next, the structure of the multi-slit element 11 will be detailed in thefollowing. As shown in FIG. 11, when the radiological image capturingapparatus 1 is used as the Talbot-Lau interferometer method, themulti-slit element 11 and the first diffraction grating 15 are apartfrom each other by the distance L. Further, for instance as detailedlater, an X ray passing through a slit 111 a, serving as one of themulti-slits of the multi-slit element 11, forms self-images of adiffraction member 152 a and a diffraction member 152 b of the firstdiffraction grating 15 on the second diffraction grating 16, which isdisposed at the position being apart from the first diffraction grating15 by the distance Z₁, (namely, on the X-ray detector 17 that is closelyadjacent to the second diffraction grating 16).

Further, another X ray passing through a slit 111 b that is located atposition adjacent to the slit 111 a also forms self-images of adiffraction member 152 a and a diffraction member 152 b of the firstdiffraction grating 15 on the second diffraction grating 16,respectively. In other words, each of the X rays passing through each ofthe slits 111 of the multi-slit element 11 forms each of self-images ofthe diffraction members 152 on the second diffraction grating 16,resulting in a striped pattern of the self-images.

On that occasion, unless a slit interval distance d₀ between the slits111 of the multi-slit element 11 is appropriate, the self-images in thestriped pattern, which are formed by the X rays passing through the slit111 a and the slit 111 b of the multi-slit element 11, counteract witheach other.

However, if the slit interval distance d₀ is adjusted, so as to make theself-image of the diffraction member 152 a, formed by the X ray passingthrough the slit 111 a, and the other self-image of the diffractionmember 152 b, formed by the X ray passing through the slit 111 b,overlap with each other at a position Y on the second diffractiongrating 16, the self-image and the other self-image in the stripedpattern can be superimposed with each other, resulting in achievement ofan in-focus state.

In the above case, the slit interval distance d₀ between the slits 111of the multi-slit element 11, the interval distance (grating period) d₁,being one of relative distances between the plural diffraction members152 of the first diffraction grating 15, the distance L between themulti-slit element 11 and the first diffraction grating 15 and thedistance Z₁ from the first diffraction grating 15 to the seconddiffraction grating 16, fulfill the Equation indicated as follow.d ₀ :d ₁=(L+Z ₁):Z ₁  (1)

Deriving from the Equation (1), the slit interval distance d₀ can berepresented by the Equation (2) indicated as follow.

$\begin{matrix}{d_{0} = {\frac{L + Z_{1}}{Z_{1}}d_{1}}} & (2)\end{matrix}$

Further, referring to FIG. 11, although there has been considered suchthe case that the X rays, passing through the slit 111 a and the slit111 b, further pass through the portions of the diffraction member 152 aand the diffraction member 152 b, which are adjacent to each other onthe first diffraction grating 15, for instance, even if the X rays passthrough the portions of the diffraction member 152 a and the diffractionmember 152 c or the diffraction member 152 d, each of which resides at aposition being apart from the diffraction member 152 a by an integralmultiple of the grating period d₁, namely, even when the Equation (3),which is indicated as follow and in which “d₁” in the Equation (2) issubstituted by “pd₁” acquired by multiplying “d₁” by “p”, is fulfilled,the self-images in the striped pattern formed on the first diffractiongrating 15 are just superimposed with each other, resulting inachievement of the in-focus state.

$\begin{matrix}{d_{0} = {\frac{L + Z_{1}}{Z_{1}}{pd}_{1}}} & (3)\end{matrix}$

Still further, since the Equation of L+Z₁+Z₂=L_(total) has beenestablished as aforementioned, and the distance Z₂ between the seconddiffraction grating 16 and the X-ray detector 17 are approximately zero,the Equation (3) can be also expressed by the Equation (4) indicated asfollow.

$\begin{matrix}{d_{0} = {\frac{Ltotal}{Z_{1}}{pd}_{1}}} & (4)\end{matrix}$

In other words, if the slits 111 of the multi-slit element 11 areappropriately formed in such a manner that the slit interval distance d₀of the slits 111 fulfills the Equation (3) and the Equation (4), the Xrays respectively passing through the slits 111 of the multi-slitelement 11 effectively form the self-images of the first diffractiongrating 15 on the second diffraction grating 16 so as to make theself-images overlap each other, and as a result, it becomes possible toacquire the self-images being in-focus.

Next, when the radiological image capturing apparatus 1 is used ineither the Talbot interferometer method or Talbot-Lau interferometermethod, the conditions that the X ray tube 8, the multi-slit element 11,the first diffraction grating 15 and the second diffraction grating 16constitute the interferometer, will be detailed in the following.

Initially, when the radiological image capturing apparatus 1 is used inthe Talbot interferometer method, the conditions that the X ray tube 8,the first diffraction grating 15 and the second diffraction grating 16constitute the interferometer will be detailed in the following.

On the premise that the first diffraction grating 15 is the phase-typediffraction grating, the distance Z₁ between the first diffractiongrating 15 and the second diffraction grating 16 should fulfill thecondition indicated as follow. In this connection, “m” represents aninteger number and “d₁” represents the interval distance, being one ofrelative distances between the plural diffraction members 152 of thefirst diffraction grating 15, as aforementioned.

$\begin{matrix}{Z_{1} = {\left( {m + \frac{1}{2}} \right)\frac{d_{1}^{2}}{\lambda}}} & (5)\end{matrix}$

Explaining the Talbot effect while referring to the schematic diagramshown in FIG. 12, in the case that the first diffraction grating 15 isthe phase-type diffraction grating, when the plane wave of the X raypasses through the first diffraction grating 15, the Talbot effect is toform the self-image of the diffraction grating at the distance given bythe Equation (5). In the state that the subject H is absence, theself-image of the first diffraction grating 15, namely, the image ofdiffraction members 152 in which the grating period for every intervaldistance d₁ is slightly expanded, emerges at such a position that isapart from the first diffraction grating 15 by the distance Z₁ given bythe Equation (5).

In this connection, at a position other that the position of thedistance Z₁ given by the Equation (5), the self-image cannot be observedor may be out of focus. However, in the vicinity of the position of thedistance Z₁ given by the Equation (5), the relatively in-focus state ofthe self-image is maintained. Accordingly, the distance Z₁ defined byEquation (5) includes allowable distances in the vicinity of thedistance Z₁. Further, when setting the actual distance Z₁, someallowance for the distance Z₁ given by the Equation (5) can beintroduced into a distance to be actually set.

Then, when the second diffraction grating 16 is positioned at a positionof the distance Z₁ in such a state that the extended direction of thediffraction members 162 is rotated relative to the other extendeddirection of diffraction members 152 of the first diffraction grating 15by a minute angle θ, Moiré fringes emerge, and the X-ray detector 17detects a Moiré stripe image M, which is formed by projecting the Moiréfringes, as shown in FIG. 7. In this case, an interval distance betweenthe Moiré stripes of the Moiré stripe image M, generated in the above,is given by d₁/θ, from the interval distance d₁ of the diffractionmembers 152 and the minute angle θ.

On the other hand, when the subject H exists between the X ray tube 8and the first diffraction grating 15, the phase of the X rays emittedfrom the X ray tube 8 would shift in mid course of passing through thesubject H. This phase sift causes a distortion of the wave front of theX rays being incident into the first diffraction grating 15.Accordingly, the self-image of the first diffraction grating 15 isdeformed, depending on the distortion of the wave front.

Successively, when the X rays diffracted by the first diffractiongrating 15 passes through the second diffraction grating 16, the Moiréstripe image M is distorted according to the distortion of the wavefront of the X rays, namely, according to the shape of the subject H. Onthat occasion, since the X rays penetrate through the inside section ofthe subject H, the X rays would be distorted by the shape of the insidesection, and accordingly, those distortions will be projected into theMoiré stripe image M.

On that occasion, actually, the self-image of the first diffractiongrating 15 is also reflected by the distortion caused by the subject H,and accordingly, at the position of the distance Z₁ given by theEquation (5), it emerges such a state that the shape of the subject Hand the shape of its inner section are reflected into the diffractionstripe of the diffraction members 152 in which the grating period forevery interval distance d₁ is slightly expanded. However, it has beenvirtually impossible for the normal-type X-ray detector 17 to detect thediffraction stripe abovementioned with its resolution capability.Accordingly, since it is also impossible to detect the distortion causedby the subject H, it has been difficult to obtain the X ray image of thesubject H as it is.

However, if the apparatus is so constituted that the second diffractiongrating 16 is rotated relative to first diffraction grating 15 by aminute angle θ so as to form such a Moiré stripe image in which theinterval distance between the stripes is far greater than the gratingperiod, it becomes possible for the normal-type X-ray detector 17 todetect the diffraction stripe abovementioned even with its resolutioncapability. Further, by employing the normal-type X-ray detector 17 fordetecting the Moiré stripe image M distorted according to the shape ofthe subject H and the shape of its inner section, it becomes possible toobtain the X ray image of the subject H, into which the shape of thesubject H and the shape of its inner section are projected.

In the radiological image capturing apparatus 1 employing the Talbotinterferometer, embodied in the present invention, as described in theforegoing, in order to heighten the coherence property of X rays emittedfrom the X ray tube 8 and having an average energy in a range of 15-60keV, as aforementioned, at the time when the concerned X rays areincident into the first diffraction grating 15, it is necessary to setthe distance L between the X ray tube 8 and the first diffractiongrating 15 at a value equal to or greater that a certain fixed distance.

As aforementioned, when the radiological image capturing apparatus 1 isused as the Talbot interferometer method, a focal point diameter “a” isset at a value equal to or greater that 1 μm. When the focal pointdiameter “a” is set at 1 μm as its minimum value and the average energyof the X rays is set at 60 keV as its maximum value, it is necessary toset the distance L between the X ray tube 8 and the first diffractiongrating 15 at a value equal to or greater that 0.5 m. However, since thecoherency (coherency distance) is in proportion to the distance L whilein inverse proportion to the average energy of the X rays and the focalpoint diameter, in the case that the coherency is acquired at 60 keV ofthe X ray average energy, for instance, the distance L between the X raytube 8 and the first diffraction grating 15 can be set at a value equalto or greater than 0.125 m (12.5 cm) as far as the average energy of theX rays is 15 keV, or, even if the focal point diameter “a” of the X raytube 8 is widened up to 4 μm, the equivalent degree of the coherency canbe obtained.

Further, although the distance Z₁ between the first diffraction grating15 and the second diffraction grating 16 is given by the Equation (5)aforementioned, as being recognizable from the fact that the Equation(5) includes the wavelength λ, the distance Z₁ depends on the averageenergy of the X rays. Accordingly, as aforementioned, when the intervaldistance d₁, being one of relative distances between the pluraldiffraction members 152 of first diffraction grating 15, is set ataround 3 μm, which is technically formable value, and the average energyof the X rays to be irradiated is set at a value in a range of 15-60keV, it is necessary to set the distance Z₁ at a value equal to orgreater than 0.05 m.

In this connection, the lower limit of the range of a value, which issettable as the distance L_(total) from X ray tube 8 to the X-raydetector 17, is specifyed by the limitations for the distance L and thedistance Z₁ (the distance Z₂ from second diffraction grating 16 to theX-ray detector 17 is zero). Further, although its upper limit is notlimited to a specific value, considering the fact that the radiologicalimage capturing apparatus 1, embodied in the present invention, would bevirtually used in the room environment, the upper limit may be set ataround 2 meters.

Next, when the radiological image capturing apparatus 1 is used in theTalbot-Lau interferometer method, the conditions that the X ray tube 8,the multi-slit element 11, the first diffraction grating 15 and thesecond diffraction grating 16 constitute the interferometer will bedetailed in the following.

Even in this case, the conditions are principally similar to those ofthe Talbot interferometer method abovementioned, the distance Z₁ betweenthe first diffraction grating 15 and the second diffraction grating 16is set at such a value that fulfills the Equation (5) aforementioned.Further, as shown in FIG. 13, each of the X rays passing through each ofthe slits 111 of the multi-slit element 11 yields the Talbot effectaforementioned. Then, each of the X rays passing through each of theslits 111 forms the self-image of the first diffraction grating 15 atthe position being apart from the first diffraction grating 15 by thedistance Z₁. On that occasion, if the slit interval distance d₀ isstructured so as to fulfill the Equation (3) and the Equation (4), theself-images just overlap with each other at the position being apartfrom the first diffraction grating 15 by the distance Z₁, resulting in ajust in-focus state.

Accordingly, when the second diffraction grating 16 is positioned at aposition of the distance Z₁ in such a state that the extended directionof the diffraction members 162 is rotated relative to the other extendeddirection of diffraction members 152 of the first diffraction grating 15by a minute angle θ, Moiré fringes emerge, and the X-ray detector 17detects the Moiré stripe image M, which is formed by projecting theMoiré fringes, as shown in FIG. 8.

On the other hand, when the subject H exists between the multi-slitelement 11 and the first diffraction grating 15, the phase of each ofthe X rays, emitted from the X ray tube 8 and passing through themulti-slit element 11, would shift in mid course of passing through thesubject H. This phase sift causes a distortion of the wave front of eachof the X rays being incident into the first diffraction grating 15.Accordingly, the self-image of the first diffraction grating 15 isdeformed, depending on the distortion of the wave front.

Successively, when each of the X rays diffracted by the firstdiffraction grating 15 passes through the second diffraction grating 16,the Moiré stripe image M is distorted according to the distortion of thewave front of each of the X rays, namely, according to the shape of thesubject H. On that occasion, since each of the X rays penetrates throughthe inside section of the subject H, each of the X rays would bedistorted by the shape of the inside section, and accordingly, thosedistortions will be projected into the Moiré stripe image M. Asdescribed in the above, by employing the normal-type X-ray detector 17for detecting the Moiré stripe image M distorted according to the shapeof the subject H and the shape of its inner section, it becomes possibleto obtain the X ray image of the subject H, into which the shape of thesubject H and the shape of its inner section are projected.

In the case that the Talbot-Lau interferometer method as abovementionedis employed, when a width of aperture of each of the slits 111 of themulti-slit element 11, corresponding to the focal point diameter of theX ray tube 8, is set at 1 μm as its minimum value and the average energyof the X rays is set at 60 keV as its maximum value, it is necessary toset the distance L between the multi-slit element 11 and the firstdiffraction grating 15 at a value equal to or greater that 0.5 m.However, since the coherency (coherency distance) is in proportion tothe distance L while in inverse proportion to the average energy of theX rays and the width of aperture of each of the slits 111, in the casethat the coherency is acquired at 60 keV of the X ray average energy,for instance, the distance L between the multi-slit element 11 and thefirst diffraction grating 15 can be set at a value equal to or greaterthan 0.125 m (12.5 cm) as far as the average energy of the X rays is 15keV, or, even if the width of aperture of each of the slits 111 iswidened up to 4 μm, the equivalent degree of the coherency can beobtained.

As well as in the case of the Talbot interferometer method, it isnecessary in the Talbot-Lau interferometer method to set the distance Z₁between first diffraction grating 15 and the second diffraction grating16 at a value equal to or greater than 0.05 m.

Further, the slit interval distance d₀ of the multi-slit element 11 hasthe relationship, represented by the aforementioned Equation (2), withrespect to the interval distance (grating period) d₁, being one ofrelative distances between the plural diffraction members 152 of thefirst diffraction grating 15, the distance L between the multi-slitelement 11 and the first diffraction grating 15, and the distance Z₁between first diffraction grating 15 and the second diffraction grating16. Accordingly, when the abovementioned limitations are applied to theinterval distance (grating period) d₁, the distance L, the distance Z₁and further, the slit width, the slit interval distance d₀ is set at avalue equal to or greater than 2 μm as its setting range.

As described in the foregoing, various kinds of setting conditions aredifferent from each other between in the case that the radiologicalimage capturing apparatus 1 is used as the Talbot interferometer methodand in the other case as the Talbot-Lau interferometer method.Accordingly, for instance as aforementioned, when detecting an abnormalshadow candidate from the captured X ray image, or when receiving theinformation in regard to an abnormal shadow candidate detected andtransmitted by the diagnosis assistance apparatus of the radiologicalimage capturing system 100, the control device 20 changes the Talbot-Lauinterferometer method, shown in FIG. 2 and FIG. 3, to the Talbotinterferometer method, in order to capture the abnormal shadow candidateas a farther sharper and clearer image.

In the above case, the control device 20 makes the multi-slit element 11rotate around the axis of the supporting bar member 7 so as to make itwithdraw from the optical path of the X rays, and at the same time,changes the angle of the target of the X ray tube so as to change thefocal point diameter of the X ray tube 8. Further, in the Talbot-Lauinterferometer method, since the objects to be adjusted are somewhatchanged, for instance, such that the distance L, which has been adjustedas the distance between the multi-slit element 11 and the firstdiffraction grating 15 in the Talbot-Lau interferometer method, isadjusted as the distance between the X ray tube 8 and the firstdiffraction grating 15 after making the multi-slit element 11 withdrawfrom the optical path of the X rays in the Talbot interferometer method,etc., the positional adjustments of the X ray tube 8, the firstdiffraction grating 15, the second diffraction grating 16 and the X-raydetector 17 are arbitrarily conducted as needed.

In the case that the Talbot interferometer method is changed to theTalbot-Lau interferometer method, the control device 20 conductsoperations being reverse to the above.

As aforementioned, when the radiological image capturing apparatus 1,embodied in the present invention, is employed for the medical use, theapparatus can merely irradiate the X rays having an average energy in arelatively narrow range of 15-60 keV. However, even in such the case, byarranging the second diffraction grating 16 and the X-ray detector 17 sothat both of them contact each other, and by specifying the distance Lbetween multi-slit element 11 and the first diffraction grating 15, thedistance Z₁ between first diffraction grating 15 and the seconddiffraction grating 16, and the slit interval distance d₀ of themulti-slit element 11 as aforementioned, it becomes possible to make theapparatus sufficiently bring out the Talbot effect so as to accuratelydetect the shapes of the subject H and its inner section in the Moiréstripe image.

Further, when the average energy of the X rays to be irradiated, issmaller than 15 keV, since almost of all part of the irradiated X raysare absorbed into the subject, a dose of X ray exposure for the subjectbecomes extremely great, and accordingly, such the setting is notsuitable for clinical use. However, by setting the average energy of theX rays at a value equal to or greater than 15 keV, it becomes possiblenot only to avoid such the problem as mentioned in the above, but alsoto obtain such the X ray image that has no blur caused by the movementof the human body, serving as the subject H, since the operation forirradiating the X rays can be completed within several per second or 2-3seconds at longest for every time of the single X-ray radiographingoperation. Further, by setting the average energy of the X rays to beirradiated at a value equal to or smaller than 60 keV, it becomespossible to acquire such the X-ray radiation image that has sufficientcontrasts so as to clearly represent bones, soft tissue sections, etc.,which constitute the human body.

As a result, even for the tissue sections, such as the cartilage tissueof the human body, etc., from which the normal-type X-ray radiographingapparatus hardly captures a clear X ray image, it becomes possible toacquire the good X ray image in which the contrast of peripheralsections of the subject is emphasized by employing the Talbot-Lauinterferometer method, and therefore, it becomes possible to effectivelyuse the clearly contrasted X ray image acquired in above for thediagnosis purpose or the like.

Further, on that occasion, by making the multi-slit element having aplurality of slits insert into or withdraw from the optical path of theX rays irradiated from the X ray tube, it becomes possible to make theTalbot interferometer method and the Talbot-Lau interferometer methodswitchable between them. In addition, by appropriately setting thedistance between the X ray source or the multi-slit element and theX-ray detector, the other distance between the X ray source or themulti-slit element and the first diffraction grating, the focal pointdiameter of the X ray tube and the slit interval distance of themulti-slit element, corresponding to each of the abovementioned methods,it becomes possible to obtain a sufficiently clear X ray image within ashort X rays irradiation time, while taking advantage of good pointspossessed by the corresponding one of methods abovementioned.

For this purpose, for instance, by employing the Talbot-Lauinterferometer method to widely radiograph the subject at first, andthen, employing the Talbot interferometer method, switched from theTalbot-Lau interferometer method, to radiograph a specific diseasedpart, etc., so as to acquire its clearer X ray image, it becomespossible to acquire a good X ray image in which the contrast ofperipheral sections of the subject is emphasized, even for theoperations for radiographing tissue sections from which the normal-typeX-ray radiographing apparatus hardly captures a clear X ray image,including not only radiographing the joint disorders, which arerepresented by the rheumatic disease, but also radiographing variouskinds of sections, such as a breast image capturing operation thatshould be capable of detecting a micro calcification from a breast, mostof which is formed by a soft tissue, an operation for radiographing achild body, almost bones of which are cartilages, etc.

Further, since the image processing apparatus 30 of the radiologicalimage capturing system 100 appropriately conducts the various kinds ofimage processing, it becomes possible to obtain not only the X ray imagebeing clearer than ever, but also the three-dimensional image of thesubject H and such the image in which a concerned lesion area isemphasized.

In this connection, instead of the configuration in which the subjectplacing plate 12, on which the subject H is to be placed, is disposedbetween the multi-slit element 11 and the first diffraction grating 15(when the apparatus is used as the Talbot interferometer method, betweenthe X ray tube 8 and the first diffraction grating 15) as structured inthe radiological image capturing apparatus 1 embodied in the presentinvention and shown in FIGS. 2 and 3, for instance, as the radiologicalimage capturing apparatus shown in FIG. 14, it is also applicable thatthe apparatus is so constituted that the subject placing plate 12, onwhich the subject H is placed, is disposed between the first diffractiongrating 15 and the second diffraction grating 16.

On that occasion, compared to the radiological image capturing apparatus1 embodied in the present invention, the first diffraction grating 15closely approaches the multi-slit element 11 and the X ray tube 8. It isnecessary that the X rays to be incident into the first diffractiongrating should have the coherency property, and for this purpose, anaperture width of each of the slits 111 (namely, a slit width, so tospeak) of the multi-slit element 11, which is to be employed when theapparatus is used as the Talbot-Lau interferometer method as shown inFIG. 14, is set at a value in a range of around 1-50 μm, and it ispreferable that the slit width is formed at a value in a range of around7-30 μm. According to the above, the X rays to be incident into thefirst diffraction grating 15 posses the coherency property and the Xrays irradiated from the X ray tube 8 are converted to the multi(plural) radiant sources.

Further, when the apparatus is used as the Talbot interferometer methodby rotating the multi-slit element 11, it becomes necessary to set thefocal point diameter “a” of the X ray tube 8 at a smaller value. Forthis reason, the focal point diameter of the X ray tube 8 is set at avalue equal to or greater than 0.1 μm, so as to make it possible toirradiate the X rays having an average energy within the abovementionedrange and to acquire the output intensity being practically available.Further, when the focal point diameter “a” is set at 1 μm as its minimumvalue and the average energy of the X rays is set at 60 keV as itsmaximum value, it is necessary to set the distance L between the X raytube 8 and the first diffraction grating 15 at a value equal to orgreater that 0.5 m. However, since the coherency (coherency distance) isin proportion to the distance L while in inverse proportion to theaverage energy of the X rays and the focal point diameter, in the casethat the coherency is acquired at 60 keV of the X ray average energy,for instance, the distance L between the X ray tube 8 and the firstdiffraction grating 15 can be set at a value equal to or greater than0.125 m (12.5 cm) as far as the average energy of the X rays is 15 keV,or, even if the focal point diameter “a” of the X ray tube 8 is widenedup to 4 μm, the equivalent degree of the coherency can be obtained. Asindicated in the schematic diagram shown in FIG. 14, since the apparatusis so constituted that the first diffraction grating 15 is disposed atthe space located between the X ray tube 8 and the subject H, it becomespossible not only to employ such the first diffraction grating 15 thatis formed within a small area, resulting in an easiness of the creationworking, but also to reduce the influence of slurs, etc., generated inthe X ray image and caused by the manufacturing variation of thediffraction grating, etc., and therefore, it becomes possible to acquirethe high-resolution X ray image being shaper than ever.

According to the present invention, the following effects can beattained.

(1) It becomes possible to make the apparatus sufficiently exhibit theTalbot effect so as to accurately detect a shape of the subject in theMoiré stripe image. On that occasion, by the converting X raysirradiated from the X ray tube to the multi (plural) radiant sources byemploying the multi-slit element, the apparatus is made to be in such astate as if micro focus X ray tubes exist in the apparatus. By employingthe multi-slit element having a sufficiently small slit width so as toacquire the Talbot effect, and by employing such an X ray tube that hasa large focal diameter so as to acquire high power X rays, it becomespossible to acquire an X ray image without blur caused by the movementsof human body, serving as the subject, only by irradiating the X rays ina short time equal to or smaller than several parts of one second. As aresult, it becomes possible not only reduce an amount of X ray exposureto be irradiated onto the human body, but also to obtain an image havinghigher contrast to such an extent that the image can be used for adiagnosis purpose.(2) By setting a distance between the multi-slit element serving asmulti radiant source and the X-ray detector 17, another distance betweenthe multi-slit element and the first diffraction grating, and a slitinterval of the multi-slit element, at appropriate values, respectively,it becomes possible to obtain a sufficiently clear X ray image even ifthe X ray irradiation time is short. Accordingly, it becomes possible toacquire a good X ray image in which the contrast of peripheral sectionsof the subject is emphasized, by employing the Talbot-Lau interferometermethod for the operations for radiographing tissue sections from whichthe normal-type X-ray radiographing apparatus hardly captures a clear Xray image, including not only radiographing the joint disorders, whichare represented by the rheumatic disease, but also radiographing variouskinds of sections, such as a breast image capturing operation thatshould be capable of detecting a micro calcification from a breast, mostof which is formed by a soft tissue, an operation for radiographing achild body, almost bones of which are cartilages, etc.

The invention claimed is:
 1. A radiological image capturing apparatus,comprising: an X ray tube that emits first X rays; a subject placingplate to place a subject thereon; a plurality of diffraction gratings;an X-ray detector that detects second X rays, which have passed throughthe plurality of diffraction gratings; and a control device thatcompares an image of Moiré fringes, which has been captured at a firstoccasion without placing the subject on the subject placing plate, withanother image of Moiré fringes, which has been captured at a secondoccasion being later than the first occasion without placing the subjecton the subject placing plate, to determine whether or not a distortionhas generated in any one of the plurality of diffraction gratings, andissues a notification when determining that the distortion has generatedin any one of the plurality of diffraction gratings.
 2. The radiologicalimage capturing apparatus of claim 1, wherein the second occasion isestablished in advance.
 3. The radiological image capturing apparatus ofclaim 2, wherein the second occasion is established based on used hoursof the radiological image capturing apparatus.
 4. A radiological imagecapturing apparatus of claim 2, wherein the second occasion isestablished based on a number of times the X ray tube emits the first Xrays.
 5. The radiological image capturing apparatus of claim 1: whereinthe second occasion is repeatedly established at predetermined timeperiods in advance.
 6. The radiological image capturing apparatus ofclaim 1, wherein the plurality of diffraction gratings includes such adiffraction grating that convert the first X rays emitted by the X raytube to multi X rays that are to be emitted from multi radiant sources.7. The radiological image capturing apparatus of claim 1, wherein thecontrol device determines that a distortion has generated in any of aplurality of gratings when, an interval of the Moire fringes is expandedor reduced at a value equal to or greater than a predetermined value; apart of or all of the Moire fringes are curved; or a difference betweena maximum part and a minimum part of detected amount of the irradiated Xrays among the Moire fringes is expanded or reduced at a value equal toor greater than a predetermined value.